1. Field of the Invention
The present invention is related to an apparatus which receives control information sent from a transmitter, and which is ideally suited for use as a remote controller in applications such as the so called keyless entry system for automobiles.
2. Description of the Prior Art
The keyless entry system is an apparatus which can control the locking and unlocking of an automobile""s doors by remote control, even from a location at some distance from the automobile. This apparatus makes it possible for someone such as the driver to carry the transmitter, and without using a key, to lock or unlock the doors and trunk etc. by remote control, through an operation such as the pressing of a push button switch on the transmitter.
In the keyless entry system, a specific set of identification data is established in advance between a transmitter and receiver which form a set. When the aforesaid push button switch is pressed, this identification data undergoes frequency modulation and is transmitted.
When the received electric field strength, detected by a squelch circuit in a standby mode, exceeds a preset threshold value, the receiver takes up the data and performs collation of the above mentioned identification data or the like. In this way, when the identification data match, the previously mentioned operations such as locking or unlocking of the doors are performed.
Thus, the receiver will produce a received response and perform door locking/unlocking control, only with respect to a control signal from a transmitter which matches the identification data registered in the receiver. Based upon this, improvements have been devised for security functions such as theft prevention.
On the one hand, theft prevention apparatuses have been extensively developed in recent years. This is the type of apparatus which detects the entry of a thief into the car without the use of a proper key, and which then generates an alarm. The current type of theft prevention apparatuses are constituted so that, for example, they detect the breaking of a window and then generate an alarm. However, a problem still remains that even if the car""s owner discovers from a distance that a thief is prowling around and is about to break into the car, he is not able to sound the alarm and prevent damage to the car before it occurs.
Accordingly, there has been a desire for a theft prevention apparatus with further improved security functions, through a combination of the keyless entry system""s transmitter and receiver with the current type of theft prevention apparatus. However, the addition of these extra functions to the transmitter and receiver would complicate their construction.
Furthermore, the previously mentioned identification data is, for example, stored in a ROM (Read Only Memory), and the transmitter and receiver are equipped with these ROM""s. Therefore, when the transmitter is lost, it is necessary to exchange the ROM in the receiver with one that matches the identification data of a new transmitter, and maintenance operations become very troublesome.
Still further, in order to avoid malfunctions at places such as parking lots, a large number of identification data combinations are created. Because of this, there is also the problem of mounting costs for the management of maintenance parts, since it is necessary for the manufacturer to maintain a stock of ROM""s which correspond to all of the identification data combinations.
Therefore, the object of the invention is to present a novel and improved receiving apparatus in order to solve the above-mentioned problems.
Another object of the invention is to present a receiving apparatus which can prevent the entry of a thief into a car before such entry occurs, by using the transmitter which controls the locking/unlocking of the car""s doors.
In order to accomplish the abovementioned objects, the present invention provides a receiving apparatus which receives communication data including an identification data from a transmitter,
means for locking/unlocking doors, and
means for controlling the locking/unlocking means when communication data matching the identification data is received. The apparatus also includes
means for determining whether or not the communication data is being continuously received for more than a preset period of time, and
means for generating an alarm when the continuous receiving condition is determined in the determining means.
Therefore, when the owner of a car discovers that a thief is about to for the owner to break into his car, it is possible to prevent the break-in before it occurs, because the alarm will be generated if the communication data is transmitted for longer than a preset period of time. Furthermore, since the transmitter which controls the locking/unlocking of the doors serves a dual purpose, costs can also be reduced.
Moreover, when a determination of continuous receiving is to be made as described above, a squelch circuit is generally used, but if this kind of circuit is added to the receiving apparatus which controls the locking/unlocking of the doors, there would be an increase in cost.
Still another object of the invention is to present a receiving apparatus having a simple construction, which can make a reliable determination of continuous receiving.
In order to accomplish the abovementioned object, a receiving apparatus of the invention which receives a communication data including an identification data from a transmitting apparatus is characterized by determining the continuous receiving condition by repeatedly performing a comparison of at least a part of the communication data and previously stored data.
In a preferred embodiment, the receiving appratus is provided with means for determining the continuous receiving when all results of the comparisons within a present period of time are matches.
Further, in a preferred embodiment, the receiving apparatus is provided with means for determining the continuous receiving condition when, there is agreement for more than a preset number of times within a number of comparisons in that period of time.
Still further, in a preferred embodiment, the receiving apparatus is provided with means for determining the continuous receiving condition and for establishing a judgment standard for each classification of the communication data. The determining means determines the continuous receiving condition when all of the judgment standards for each classification are satisfied within a preset period of time as a result of the comparisons within the preset period of time.
In accordance with the invention, continuous the receiving condition is determined by a repeated comparison of at least a part of the communication data with the previously stored data, in a radiocommunication type receiving apparatus that does not have a squelch circuit. Therefore, the determination of the continuous receiving condition can be realized with a simple construction, without using a special construction such as a squelch circuit in a frequency modulation system. Further, since a comparison is performed between the communication data for which the continuous receiving condition determination is made, and the previously stored data, it is possible to prevent errors in the receiving of data.
Still another object of the invention is to present a receiving apparatus with a simple construction making possible easy performance of writing, clearing and reading out of identification data, which can reduce maintenance costs.
In order to accomplish the above-mentioned object, a which receives apparatus of the invention receiving a communication data including an identification data from a transmitting apparatus, comprises
means for storing, which makes possible the writing, clearing and reading out of the identification data,
means for status setting to set the storing means to writable status, clearable status or readable status, and
means for controlling in response to an output from the status setting means.
When the storing means is set to the writable status, the means for controlling receives the communication data from the transmitting apparatus, and writes the identification data contained in the received communication data to the storing means.
When the storing means is set to the clearable status, the means for controlling clears the identification data stored in the storing means. When the storing means is set to the readable status, the means for controlling reads out the identification data from the storing means, and when the identification data that is read out matches the identification data contained in the received communication data, the means for controlling outputs an output signal which responds to the received communication data.
In a preferred embodiment, the receiving apparatus is provided with means for reporting which reports over the period of the status that the storing means is in the writable status.
Further, in a preferred embodiment, the status setting means includes means for switching the writable status and the readable status, and means for clocking the period after the switching means has operated.
The status setting means sets into a status indicates that the switching means has been operated when a preset period of time has passed after the switching means is operated. The status setting means sets into the clearable status when, after the switching means is operated, the switching means is operated again before the time period has passed.
Still further in a preferred embodiment, the storing means is divided into a number of storing areas, and if the inputted identification data exceeds the number of divisions, the identification data is cleared in the order of the earliest input to the storing means.
In accordance with the invention, a storing means which can write, clear (i.e., erase) and read out the identification data, is provided in a receiving apparatus that receives a communication data, including an identification data, from a transmitting apparatus. A storing means is set to either a writable status, a clearable status or a readable status by a status setting means.
For example, when the storing means is set to the writable status, a controlling means receives the communication data from the transmitting apparatus, and registers the identification data contained in the received communication data by writing it into the storing means.
In this way the written identification data is read out each time the controlling means receives communication data when the storing means is set to the readable status. The written identification data is compared with the identification data contained in the received communication data. When, as a result of this comparison both are in agreement, the controlling means outputs an output signal based upon the received communication data.
Therefore, it is possible to write and register specific identification data with a simple construction. Based upon this, it is possible to devise maintenance cost reductions through the common use of parts, because it is not necessary to make the storing means correspond individually with identification data from the transmitting apparatus. It is also possible to make receiving apparatuses equipped with a common storing means to correspond individually with a number of transmitting apparatuses, each having different identification data.
Moreover, because it has been made possible to clear the stored contents of the storing means, when data communication is not needed, the response to communication from the transmitting apparatus can be stopped by clearing the stored contents. Based upon this, security functions can be improved since theft can be prevented before such theft occurs.